Heat sink for a lamp



FIG. 1 is a perspective view of the design for a heat sink for a lamp as seen from the front, top;

FIG. 2 is a rear perspective view as seen from the rear, side thereof;

FIG. 3 is a side elevational view thereof;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a rear plan view thereof.

The broken line disclosure is for environmental purposes only and does not form a part of the claimed design. 

CLAIM The ornamental design for a heat sink for a lamp, as shown and described. 